1. Field of the Invention
The present invention relates to a frame body for use in winding a coil for a deflection yoke mounted on television receivers or display units, etc.
2. Description of the Prior Art
In recent years, development of television receivers into high-resolution and highly fine display units, increasingly tend to demand strict specifications relating to color mismatching, i.e., convergence of the cathode-ray tube screen of these apparatus. Under such tendency, it is earnestly desired that a deflection magnetic field be controlled more precisely.
A deflection yoke mounted on a cathode ray tube of a television receiver or display unit is generally composed of a bobbin 2 as a funnel-shaped winding frame body, with horizontal deflection coils attached to the bobbin 2 on its inner side at both top and bottom, and with vertical deflection coils attached to the outside of the bobbin 2.
FIG. 1 shows an example of a bobbin for a saddle type deflection coil for use in a typical deflection yoke. The bobbin 2 is provided with a plurality of coil-winding grooves 5, on which, for example, a coiling wire 11 is wound in layers as shown in FIG. 2, to thereby form a deflection coil. The coiling wire 11 is a conductive wire (such as litz wires for example) with an insulating layer 4. In winding the coiling wire 11 on the aforementioned coil-winding grooves 5, the coiling wire 11 is wound in layers by an automatic winding machine, one by one, or by every some number of wires, thereby producing a deflection coil.
Such prior art deflection coil, however, suffers from drawbacks. Variation in directions of the stretching force acted on coiling wire 11 as it was wound may have caused displacement and biasing as shown in FIG. 2. In other cases, the order of winding of coiling wire 11 can be altered and hence such winding as previously designated by a design instruction cannot be effected. Further, the biased states of coiling wire 11 of deflection coils that are mass-produced differ from one another. Therefore, it would be impossible to regulate a deflection field with high precision. Additionally, mass-production makes variations in winding larger, resulting in lowering of the yield, and hence the prior art winding method is disadvantageous in view of cost. Even in the just-mentioned prior art method, the displacement and biased state of the coiling wire 11 wound can be reduce for satisfy the original design as the width of the coil-winding grooves is narrowed, but this results in coil performance deteriorization because, of the ratio L/R between inductance L and resistance R being reduced.
In order to eliminate such problems, the present applicant has previously proposed a deflection coil which is formed using a wire ribbon in place of winding a single wire one by one as used to be practiced.
Examples of wire ribbon 15 include one that is composed as shown in FIG. 3A by arranging in parallel a plurality of conductive wires 8 of copper, aluminum or the like with an insulating layer 4 coated thereon, and adhering them using an adhesive 6. Another wire ribbon is composed as shown in FIG. 3B by arranging in parallel a plurality of conductive wires 8 with an insulating layer 4 coated thereon, and adhering together the wires on one side of an insulator sheet 7 made of resin, etc., with an adhesive 6. A further wire ribbon is composed as shown in FIG. 3C by arranging and adhering together in parallel a plurality of conductive wires 8 formed with an insulating layer 4 and an adhesive layer 9.
The conductive wires 8 forming the aforementioned wire ribbon 15 are arranged and fixed in parallel with one another in an orderly manner in a row, and therefore, neither will each conductive wire 8 be displaced in wire ribbon 15, nor will the order of the wires be altered. Therefore, when this wire ribbon 15 is used, namely, the wire ribbon 15 is wound in layers, it is possible to produce a deflection coil free from the aforementioned problems such as significant displacement of the conductive wires 8, and the like.
The production of such a deflection coil as described above is achieved by inserting the wire ribbon into a coil-winding groove 5 having a flange 3 so as to wind it in layers along a bottom face 10 of the groove 5.
Meanwhile, the bobbin 2 has a coil-winding frame body on which the wire ribbon 15 is wound, comprising a straight portion S on its neck side N and a curved surface portion R spreading outward from the end of the straight portion S toward its head side H. There are provided a plurality of coil-winding grooves 5 on the inner face of the curved surface portion elongated from the neck side to the head side H. Of these grooves, one particular coiling groove in the straight portion S (to be referred to as a main groove 5e) becomes divided in the curved surface portion R into a plurality of branch grooves (in this example, three branch grooves 5f, 5g and 5h).
In the prior art coil-winding frame body having a structure described above, the branch groove thus divided used to be formed so as to be wider than a wire ribbon used by leaving a margin equal to the dimensional tolerance of the ribbon, and points at which branch grooves branch off the main groove would vary. For this reason, when the wire ribbon 15 were wound in layers onto the coil-winding grooves constructed as above, the wire ribbon 15 would be displaced or biased in the width direction. Further, since the starting points at which the branch grooves 5f, 5g and 5h branch off the main groove 5e were different or unregulated in position, the wire ribbon 15 would come in contact with edges of the groove side walls, etc., at branching points and therefore could not enter the groove smoothly. Accordingly, the wire ribbon could be twisted at the contact point while being wound, thus giving rise to a problem that the dimensional accuracy would be deteriorated. Hence, it has been difficult for the thus constructed deflection coil to control a deflection magnetic field with precision.